1. Field of the Invention
The present invention relates to a process for bend-shaping a glass plate so that the glass plate has a complexly curved face and an apparatus for carrying out the process.
2. Discussion of Background
In automobile industries, there has been an increasing demand for a glass plate having a complexly curved face, i.e. a glass plate 8 having a complexly curved face wherein a flat glass plate is bend-shaped with two different radius of curvatures R1 and R2 in its longitudinal and transversal directions as shown in FIG. 3.
FIG. 4 shows an example of a bend-shaping apparatus proposed as an apparatus for bend-shaping a glass plate to have a complexly curved face (Japanese Examined Patent Publication No. 10331/1974). With use of a bend-shaping apparatus 10, a glass plate 8 is bend-shaped to have a radius R2 along the axis perpendicular to the transferring direction while it is transferred on hearth beds 13, 13 and then, the glass plate 8 is bend-shaped to have a radius R1 along the axis of the transferring direction on hearth beds 14, 16 each of which has a portion curved along the axis of the transferring direction, and then it is cooled and strengthened at a blowing port 18, whereby a complexly curved face is formed in the glass plate 8 as shown in FIG. 3.
A shaping furnace constitutes a very large portion of the investment for such glass manufacture line. Accordingly, it is advantageous if equipment for a conventional glass plate manufacture line for producing a glass plate having a simply curved face can be used for a glass plate manufacture line which is used for producing a glass plate having a complexly curved face. In particular, it is advantageous if the shaping furnace for the conventional manufacture line can be used in common. However, there were many difficulties in using the same shaping furnace for both types of curved glass plates. Namely, when it is desired that the glass plate manufacture line for a glass plate having a simply curved face, which is already equipped, is used for a glass plate manufacture line for a glass plate having a complexly curved face as shown in FIG. 4, it is necessary to replace the hearth beds 14, 16 and the blowing port 18 in the glass plate manufacture line for a glass plate having a simply curved face by those for a glass plate having a complexly curved face. In the conventional bend-shaping apparatus for producing a glass plate having a complexly curved face, however, there was a large distance in the vertical direction between the level H2 of the position where the glass plate is not yet bend-shaped and the level H1 of the position where the glass plate has been bend-shaped. The distance is indicated by H in FIG. 4. Namely, if the shaping furnace of the glass plate manufacture line for a glass plate having a simple curved face is to be used in common for the glass plate manufacture line for a glass plate having a complexly curved face, it is necessary to provide a special raising means for raising a glass plate, which has been bend-shaped in the longitudinal direction, from the lower level H1 to the higher level H2 in a case that the glass plate having a complexly curved face is to be manufactured.
The lower level H1 varies depending not only on the difference between the nature of the glass plate having a simply curved face and the nature of the glass plate having a complexly curved face but also on the specification of the glass plate having the complexly curved face. Namely, such raising means has to be either of an inclusive use which is separately prepared depending on the specification for bend-shaping the glass plate, or has to be used after the adjustment of an existing raising means depending on the specification. The preparation of several types of raising means for inclusive use depending on the type of glass plate is not preferable because a large investment for equipment is required. The adjustment of the existing raising means is not practical because much time and labor are required when the type of glass plate to be manufactured is changed. In addition, in practice, there are many difficulties in the technical viewpoint to raise the glass plate from the lower level Hi to the higher level H2.
Namely, in the conventional glass plate bend-shaping line for bend-shaping a glass plate having a simple curved face, the distance L between a shaping furnace 12 and a post-treating conveyor 20 is determined to be short (generally, several meters or shorter) in order to reduce equipment space as much as possible. Accordingly, when the shaping furnace in the existing glass plate shaping line for a glass plate having a simply curved face is used for the production of a glass plate having a complexly curved face, it is necessary to raise the glass plate from the lower level H1 to the higher level H2 in the relatively short distance L.
In such conditions, it is very difficult to stably transfer the glass plate in that distance because the radius of curvature and the gradient of the transferring surface of the blowing port 18 are different from those of the transferring surface of the raising means. Such difficulty can be eliminated if the distance L can be enlarged to more than 10 meters. However, this does not meet the demand of saving space, and it is impossible to use the existing manufacture line for a glass plate having a simple curved face for the manufacture line for a glass plate having a complexly curved face.